U.S. patent application number 11/117510 was filed with the patent office on 2005-08-25 for lamp monitoring and control system and method.
Invention is credited to Williams, Larry, Young, Michael F..
Application Number | 20050184671 11/117510 |
Document ID | / |
Family ID | 25276768 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050184671 |
Kind Code |
A1 |
Williams, Larry ; et
al. |
August 25, 2005 |
Lamp monitoring and control system and method
Abstract
A system and method for remotely monitoring and/or controlling
an apparatus and specifically for remotely monitoring and/or
controlling street lamps. The lamp monitoring and control system
comprises lamp monitoring and control units, each coupled to a
respective lamp to monitor and control, and each transmitting
monitoring data having at least an ID field and a status field; and
at least one base station, coupled to a group of the lamp
monitoring and control units, for receiving the monitoring data,
wherein each of the base stations includes an ID and status
processing unit for processing the ID field of the monitoring
data.
Inventors: |
Williams, Larry; (Los
Angeles, CA) ; Young, Michael F.; (Falls Church,
VA) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. Box 221200
Chantilly
VA
20153-1200
US
|
Family ID: |
25276768 |
Appl. No.: |
11/117510 |
Filed: |
April 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11117510 |
Apr 29, 2005 |
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10834869 |
Apr 30, 2004 |
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6892168 |
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10834869 |
Apr 30, 2004 |
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10628353 |
Jul 29, 2003 |
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6807516 |
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10628353 |
Jul 29, 2003 |
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10118324 |
Apr 9, 2002 |
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6604062 |
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10118324 |
Apr 9, 2002 |
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09576545 |
May 22, 2000 |
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6370489 |
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09576545 |
May 22, 2000 |
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09465795 |
Dec 17, 1999 |
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6415245 |
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09465795 |
Dec 17, 1999 |
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08838303 |
Apr 16, 1997 |
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6035266 |
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Current U.S.
Class: |
315/119 |
Current CPC
Class: |
H05B 47/19 20200101;
H05B 47/22 20200101; H05B 47/175 20200101 |
Class at
Publication: |
315/119 |
International
Class: |
H05B 037/00 |
Claims
What is claimed is:
1. A system for communication information related to a plurality of
remote devices, comprising: a plurality of monitoring and control
units, each such monitoring and control unit being secured and
operably connected to one of said remote devices, each such
monitoring and control unit comprising a wireless communication
device; and at least one area control station positioned to
wirelessly communicate with said plurality of remote devices.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of application
Ser. No. 10/834,869, filed Apr. 30, 2004, which is a Continuation
of Ser. No. 10/628,353 filed Jul. 29, 2003, (now U.S. Pat. No.
6,807,516) which is a continuation of application Ser. No.
10/118,324 filed Apr. 9, 2002 (now U.S. Pat. No. 6,604,062); which
is a continuation of application Ser. No. 09/576,545 filed May 22,
2000 (now U.S. Pat. No. 6,370,489); which is a division of
application Ser. No. 09/465,795 filed Dec. 17, 1999 (now U.S. Pat.
No. 6,415,245); which is a division of application Ser. No.
08/838,303 filed Apr. 16, 1997 (now U.S. Pat. No. 6,035,266). The
entire disclosure of the prior applications is considered as being
part of the disclosure of the accompanying application and is
hereby incorporated by reference therein.
BACKGROUND
[0002] This invention relates generally to a system and method for
remotely monitoring and/or controlling an apparatus and
specifically to a lamp monitoring and control system and method for
use with street lamps.
[0003] The first street lamps were used in Europe during the latter
half of the seventeenth century. These lamps consisted of lanterns
which were attached to cables strung across the street so that the
lantern hung over the center of the street. In France, the police
were responsible for operating and maintaining these original
street lamps while in England contractors were hired for street
lamp operation and maintenance. In all instances, the operation and
maintenance of street lamps was considered a government
function.
[0004] The operation and maintenance of street lamps, or more
generally any units which are distributed over a large geographic
area, can be divided into two tasks: monitor and control.
Monitoring comprises the transmission of information from the
distributed unit regarding the unit's status and controlling
comprises the reception of information by the distributed unit.
[0005] For the present example in which the distributed units are
street lamps, the monitoring function comprises periodic checks of
the street lamps to determine if they are functioning properly. The
controlling function comprises turning the street lamps on at night
and off during the day.
[0006] This monitor and control function of the early street lamps
was very labor intensive since each street lamp had to be
individually lit (controlled) and watched for any problems
(monitored). Because these early street lamps were simply lanterns,
there was no centralized mechanism for monitor and control and both
of these functions were distributed at each of the street
lamps.
[0007] Eventually, the street lamps were moved from the cables
hanging over the street to poles which were mounted at the side of
the street. Additionally, the primitive lanterns were replaced with
oil lamps.
[0008] The oil lamps were a substantial improvement over the
original lanterns because they produced a much brighter light. This
resulted in illumination of a greater area by each street lamp.
Unfortunately, these street lamps still had the same problem as the
original lanterns in that there was no centralized monitor and
control mechanism to light the street lamps at night and watch for
problems.
[0009] In the 1840's, the oil lamps were replaced by gaslights in
France. The advent of this new technology began a government
centralization of a portion of the control function for street
lighting since the gas for the lights was supplied from a central
location.
[0010] In the 1880's, the gaslights were replaced with electrical
lamps. The electrical power for these street lamps was again
provided from a central location. With the advent of electrical
street lamps, the government finally had a centralized method for
controlling the lamps by controlling the source of electrical
power.
[0011] The early electrical street lamps were composed of arc lamps
in which the illumination was produced by an arc of electricity
flowing between two electrodes.
[0012] Currently, most street lamps still use arc lamps for
illumination. The mercury-vapor lamp is the most common form of
street lamp in use today. In this type of lamp, the illumination is
produced by an arc which takes place in a mercury vapor.
[0013] FIG. 1 shows the configuration of a typical mercury-vapor
lamp. This figure is provided only for demonstration purposes since
there are a variety of different types of mercury-vapor lamps.
[0014] The mercury-vapor lamp consists of an arc tube 110 which is
filled with argon gas and a small amount of pure mercury. Arc tube
110 is mounted inside a large outer bulb 120 which encloses and
protects the arc tube. Additionally, the outer bulb may be coated
with phosphors to improve the color of the light emitted and reduce
the ultraviolet radiation emitted. Mounting of arc tube 110 inside
outer bulb 120 may be accomplished with an arc tube mount support
130 on the top and a stem 140 on the bottom.
[0015] Main electrodes 150a and 150b, with opposite polarities, are
mechanically sealed at both ends of arc tube 110. The mercury-vapor
lamp requires a sizeable voltage to start the arc between main
electrodes 150a and 150b.
[0016] The starting of the mercury-vapor lamp is controlled by a
starting circuit (not shown in FIG. 1) which is attached between
the power source (not shown in FIG. 1) and the lamp. Unfortunately,
there is no standard starting circuit for mercury-vapor lamps.
After the lamp is started, the lamp current will continue to
increase unless the starting circuit provides some means for
limiting the current. Typically, the lamp current is limited by a
resistor, which severely reduces the efficiency of the circuit, or
by a magnetic device, such as a choke or a transformer, called a
ballast.
[0017] During the starting operation, electrons move through a
starting resistor 160 to a starting electrode 170 and across a
short gap between starting electrode 170 and main electrode 150b of
opposite polarity. The electrons cause ionization of some of the
Argon gas in the arc tube. The ionized gas diffuses until a main
arc develops between the two opposite polarity main electrodes 150a
and 150b. The heat from the main arc vaporizes the mercury droplets
to produce ionized current carriers. As the lamp current increases,
the ballast acts to limit the current and reduce the supply voltage
to maintain stable operation and extinguish the arc between main
electrode 150b and starting electrode 170.
[0018] Because of the variety of different types of starter
circuits, it is virtually impossible to characterize the current
and voltage characteristics of the mercury-vapor lamp. In fact, the
mercury-vapor lamp may require minutes of warm-up before light is
emitted. Additionally, if power is lost, the lamp must cool and the
mercury pressure must decrease before the starting arc can start
again.
[0019] The mercury-vapor lamp has become one of the predominant
types of street lamp with millions of units produced annually. The
current installed base of these street lamps is enormous with more
than 500,000 street lamps in Los Angeles alone. The mercury-vapor
lamp is not the most efficient gaseous discharge lamp, but is
preferred for use in street lamps because of its long life,
reliable performance, and relatively low cost.
[0020] Although the mercury-vapor lamp has been used as a common
example of current street lamps, there is increasing use of other
types of lamps such as metal halide and high pressure sodium. All
of these types of lamps require a starting circuit which makes it
virtually impossible to characterize the current and voltage
characteristics of the lamp.
[0021] FIG. 2 shows a lamp arrangement 201 with a typical lamp
sensor unit 210 which is situated between a power source 220 and a
lamp assembly 230. Lamp assembly 230 includes a lamp 240 (such as
the mercury-vapor lamp presented in FIG. 1) and a starting circuit
250.
[0022] Most cities currently use automatic lamp control units to
control the street lamps. These lamp control units provide an
automatic, but decentralized, control mechanism for turning the
street lamps on at night and off during the day.
[0023] A typical street lamp assembly 201 includes a lamp sensor
unit 210 which in turn includes a light sensor 260 and a relay 270
as shown in FIG. 2. Lamp sensor unit 210 is electrically coupled
between external power source 220 and starting circuit 250 of lamp
assembly 230. There is a hot line 280a and a neutral line 280b
providing electrical connection between power source 220 and lamp
sensor unit 210. Additionally, there is a switched line 280c and a
neutral line 280d providing electrical connection between lamp
sensor unit 210 and starting circuit 250 of lamp assembly 230.
[0024] From a physical standpoint, most lamp sensor units 210 use a
standard three prong plug, for example a twist lock plug, to
connect to the back of lamp assembly 230. The three prongs couple
to hot line 280a, switched line 280c, and neutral lines 280b and
280d. In other words, the neutral lines 280b and 280d are both
connected to the same physical prong since they are at the same
electrical potential. Some systems also have a ground wire, but no
ground wire is shown in FIG. 2 since it is not relevant to the
operation of lamp sensor unit 210.
[0025] Power source 220 may be a standard 115 Volt, 60 Hz source
from a power line. Of course, a variety of alternatives are
available for power source 220. In foreign countries, power source
220 may be a 220 Volt, 50 Hz source from a power line.
Additionally, power source 220 may be a DC voltage source or, in
certain remote regions, it may be a battery which is charged by a
solar reflector.
[0026] The operation of lamp sensor unit 210 is fairly simple. At
sunset, when the light from the sun decreases below a sunset
threshold, light sensor 260 detects this condition and causes relay
270 to close. Closure of relay 270 results in electrical connection
of hot line 280a and switched line 280c with power being applied to
starting circuit 250 of lamp assembly 230 to ultimately produce
light from lamp 240. At sunrise, when the light from the sun
increases above a sunrise threshold, light sensor 260 detects this
condition and causes relay 270 to open. Opening of relay 270
eliminates electrical connection between hot line 280a and switched
line 280c and causes the removal of power from starting circuit 250
which turns lamp 240 off.
[0027] Lamp sensor unit 210 provides an automated, distributed
control mechanism to turn lamp assembly 230 on and off.
Unfortunately, it provides no mechanism for centralized monitoring
of the street lamp to determine if the lamp is functioning
properly. This problem is particularly important in regard to the
street lamps on major boulevards and highways in large cities. When
a street lamp burns out over a highway, it is often not replaced
for a long period of time because the maintenance crew will only
schedule a replacement lamp when someone calls the city maintenance
department and identifies the exact pole location of the bad lamp.
Since most automobile drivers will not stop on the highway just to
report a bad street lamp, a bad lamp may go unreported
indefinitely.
[0028] Additionally, if a lamp is producing light but has a hidden
problem, visual monitoring of the lamp will never be able to detect
the problem. Some examples of hidden problems relate to current,
when the lamp is drawing significantly more current than is normal,
or voltage, when the power supply is not supplying the appropriate
voltage level to the street lamp.
[0029] Furthermore, the present system of lamp control in which an
individual light sensor is located at each street lamp, is a
distributed control system which does not allow for centralized
control. For example, if the city wanted to turn on all of the
street lamps in a certain area at a certain time, this could not be
done because of the distributed nature of the present lamp control
circuits.
[0030] Because of these limitations, a new type of lamp monitoring
and control system is needed which allows centralized monitoring
and/or control of the street lamps in a geographical area.
[0031] One attempt to produce a centralized control mechanism is a
product called the RadioSwitch made by Cetronic. The RadioSwitch is
a remotely controlled time switch for installation on the DIN-bar
of control units. It is used for remote control of electrical
equipment via local or national paging networks. Unfortunately, the
RadioSwitch is unable to address most of the problems listed
above.
[0032] Since the RadioSwitch is receive only (no transmit
capability), it only allows one to remotely control external
equipment. Furthermore, since the communication link for the
RadioSwitch is via paging networks, it is unable to operate in
areas in which paging does not exist (for example, large rural
areas in the United States). Additionally, although the RadioSwitch
can be used to control street lamps, it does not use the standard
three prong interface used by the present lamp control units.
Accordingly, installation is difficult because it cannot be used as
a plug-in replacement for the current lamp control units.
[0033] Because of these limitations of the available equipment,
there exists a need for a new type of lamp monitoring and control
system which allows centralized monitoring and/or control of the
street lamps in a geographical area. More specifically, this new
system must be inexpensive, reliable, and able to handle the
traffic generated by communication with the millions of currently
installed street lamps.
[0034] Although the above discussion has presented street lamps as
an example, there is a more general need for a new type of
monitoring and control system which allows centralized monitoring
and/or control of units distributed over a large geographical
area.
[0035] The above references are incorporated by reference herein
where appropriate for appropriate teachings of additional or
alternative details, features and/or technical background.
SUMMARY OF THE INVENTION
[0036] The present invention provides a lamp monitoring and control
system and method for use with street lamps which solves the
problems described above.
[0037] While the invention is described with respect to use with
street lamps, it is more generally applicable to any application
requiring centralized monitoring and/or control of units
distributed over a large geographical area.
[0038] Accordingly, an object of the present invention is to
provide a system for monitoring and controlling lamps or any remote
device over a large geographical area.
[0039] Another object of the invention is to provide a method for
randomizing transmit times and channel numbers to reduce the
probability of a packet collision.
[0040] An additional object of the present invention is to provide
a base station for receiving monitoring data from remote
devices.
[0041] Another object of the current invention is to provide an ID
and status processing unit in the base station for processing an ID
and status field in the monitoring data and allowing storage in a
database to create statistical profiles.
[0042] An advantage of the present invention is that it solves the
problem of efficiently providing centralized monitoring and/or
control of the street lamps in a geographical area.
[0043] Another advantage of the present invention is that by
randomizing the frequency and timing of redundant transmissions, it
reduces the probability of collisions while increasing the
probability of a successful packet reception.
[0044] An additional advantage of the present invention is that it
provides for a new type of monitoring and control unit which allows
centralized monitoring and/or control of units distributed over a
large geographical area.
[0045] Another advantage of the present invention is that it allows
bases stations to be connected to other base stations or to a main
station in a network topology to increase the amount of monitoring
data in the overall system.
[0046] A feature of the present invention, in accordance with one
embodiment, is that it includes the base station with an ID and
status processing unit for processing the ID field of the
monitoring data.
[0047] Another feature of the present invention is that in
accordance with an embodiment, the monitoring data further includes
a data field which can store current or voltage data in a lamp
monitoring and control system.
[0048] An additional feature of the present invention, in
accordance with another embodiment, is that it includes remote
device monitoring and control units which can be linked to the
bases station via RF, wire, coaxial cable, or fiber optics.
[0049] These and other objects, advantages and features can be
accomplished in accordance with the present invention by the
provision of a lamp monitoring and control system comprising lamp
monitoring and control units, each coupled to a respective lamp to
monitor and control, and each transmitting monitoring data having
at least an ID field and a status field; and at least one base
station, coupled to a group of the lamp monitoring and control
units, for receiving the monitoring data, wherein each of the base
stations includes an ID and status processing unit for processing
the ID field of the monitoring data.
[0050] These and other objects, advantages and features can
additionally be accomplished in accordance with the present
invention by the provision of a remote device monitoring and
control system comprising remote device monitoring and control
units, each coupled to a respective remote device to monitor and
control, and each transmitting monitoring data having at least an
ID field and a status field; and at least one base station, coupled
to a group of the remote device monitoring and control units, for
receiving the monitoring data, wherein each of the base stations
includes an ID and status processing unit for processing the ID
field of the monitoring data.
[0051] These and other objects, advantages and features can also be
accomplished in accordance with the present invention by the
provision of a method for monitoring the status of lamps,
comprising the steps of collecting monitoring data for the lamps
and transmitting the monitoring data.
[0052] Additional objects, advantages, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from practice of the invention. The objects and advantages
of the invention may be realized and attained as particularly
pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] The invention will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements wherein:
[0054] FIG. 1 shows the configuration of a typical mercury-vapor
lamp.
[0055] FIG. 2 shows a typical configuration of a lamp arrangement
comprising a lamp sensor unit situated between a power source and a
lamp assembly.
[0056] FIG. 3 shows a lamp arrangement, according to one embodiment
of the invention, comprising a lamp monitoring and control unit
situated between a power source and a lamp assembly.
[0057] FIG. 4 shows a lamp monitoring and control unit, according
to another embodiment of the invention, including a processing and
sensing unit, a TX unit, and an RX unit.
[0058] FIG. 5 shows a general monitoring and control unit,
according to another embodiment of the invention, including a
processing and sensing unit, a TX unit, and an RX unit.
[0059] FIG. 6 shows a monitoring and control system, according to
another embodiment of the invention, including a base station and a
plurality of monitoring and control units.
[0060] FIG. 7 shows a monitoring and control system, according to
another embodiment of the invention, including a plurality of base
stations, each having a plurality of associated monitoring and
control units.
[0061] FIG. 8 shows an example frequency channel plan for a
monitoring and control system, according to another embodiment of
the invention.
[0062] FIGS. 9A-B show packet formats, according to another
embodiment of the invention, for packet data between the monitoring
and control unit and the base station.
[0063] FIG. 10 shows an example of bit location values for a status
byte in the packet format, according to another embodiment of the
invention.
[0064] FIGS. 11A-C show a base station for use in a monitoring and
control system, according to another embodiment of the
invention.
[0065] FIG. 12 shows a monitoring and control system, according to
another embodiment of the invention, having a main station coupled
through a plurality of communication links to a plurality of base
stations.
[0066] FIG. 13 shows a base station, according to another
embodiment of the invention.
[0067] FIGS. 14A-E show a method for one implementation of logic
for a monitoring and control system, according to another
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0068] The preferred embodiments of a lamp monitoring and control
system (LMCS) and method, which allows centralized monitoring
and/or control of street lamps, will now be described with
reference to the accompanying figures. While the invention is
described with reference to an LMCS, the invention is not limited
to this application and can be used in any application which
requires a monitoring and control system for centralized monitoring
and/or control of devices distributed over a large geographical
area. Additionally, the term street lamp in this disclosure is used
in a general sense to describe any type of street lamp, area lamp,
or outdoor lamp.
[0069] FIG. 3 shows a lamp arrangement 301 which includes lamp
monitoring and control unit 310, according to one embodiment of the
invention. Lamp monitoring and control unit 310 is situated between
a power source 220 and a lamp assembly 230. Lamp assembly 230
includes a lamp 240 and a starting circuit 250.
[0070] Power source 220 may be a standard 115 volt, 60 Hz source
supplied by a power line. It is well known to those skilled in the
art that a variety of alternatives are available for power source
220. In foreign countries, power source 220 may be a 220 volt, 50
Hz source from a power line. Additionally, power source 220 may be
a DC voltage source or, in certain remote regions, it may be a
battery which is charged by a solar reflector.
[0071] Recall that lamp sensor unit 210 included a light sensor 260
and a relay 270 which is used to control lamp assembly 230 by
automatically switching the hot line 280a to a switched line 280c
depending on the amount of ambient light received by light sensor
260.
[0072] On the other hand, lamp monitoring and control unit 310
provides several functions including a monitoring function which is
not provided by lamp sensor unit 210. Lamp monitoring and control
unit 310 is electrically located between the external power supply
220 and starting circuit 250 of lamp assembly 230. From an
electrical standpoint, there is a hot line 280a and a neutral line
280b between power supply 220 and lamp monitoring and control unit
310. Additionally, there is a switched line 280c and a neutral line
280d between lamp monitoring and control unit 310 and starting
circuit 250 of lamp assembly 230.
[0073] From a physical standpoint, lamp monitoring and control unit
310 may use a standard three-prong plug to connect to the back of
lamp assembly 230. The three prongs in the standard three-prong
plug represent hot line 280a, switched line 280c, and neutral lines
280b and 280d. In other words, the neutral lines 280b and 280d are
both connected to the same physical prong and share the same
electrical potential.
[0074] Although use of a three-prong plug is recommended because of
the substantial number of street lamps using this type of standard
plug, it is well known to those skilled in the art that a variety
of additional types of electrical connection may be used for the
present invention. For example, a standard power terminal block or
AMP power connector may be used.
[0075] FIG. 4 includes lamp monitoring and control unit 310, the
operation of which will be discussed in more detail below along
with particular embodiments of the unit. Lamp monitoring and
control unit 310 includes a processing and sensing unit 412, a
transmit (TX) unit 414, and an optional receive (RX) unit 416.
Processing and sensing unit 412 is electrically connected to hot
line 280a, switched line 280c, and neutral lines 280band 280d.
Furthermore, processing and sensing unit 412 is connected to TX
unit 414 and RX unit 416. In a standard application, TX unit 414
may be used to transmit monitoring data and RX unit 416 may be used
to receive control information. For applications in which external
control information is not required, RX unit 416 may be omitted
from lamp monitoring and control unit 310.
[0076] FIG. 5 shows a general monitoring and control unit 510
including a processing and sensing unit 520, a TX unit 530, and an
optional RX unit 540. Monitoring and control unit 510 differs from
lamp monitoring and control unit 310 in that monitoring and control
unit 510 is general-purpose and not limited to use with street
lamps. Monitoring and control unit 510 can be used to monitor and
control any remote device 550.
[0077] Monitoring and control unit 510 includes processing and
sensing unit 520 which is coupled to remote device 550. Processing
and sensing unit 520 is further coupled to TX unit 530 for
transmitting monitoring data and may be coupled to an optional RX
unit 540 for receiving control information.
[0078] FIG. 6 shows a monitoring and control system 600, according
to one embodiment of the invention, including a base station 610
and a plurality of monitoring and control units 510a-d.
[0079] Monitoring and control units 510a-d each correspond to
monitoring and control unit 510 as shown in FIG. 5, and are coupled
to a remote device 550 (not shown in FIG. 6) which is monitored and
controlled. Each of monitoring and control units 510a-d can
transmit monitoring data through its associated TX unit 530 to base
station 610 and receive control information through a RX unit 540
from base station 610.
[0080] Communication between monitoring and control units 510a-d
and base station 610 can be accomplished in a variety of ways,
depending on the application, such as using: RF, wire, coaxial
cable, or fiber optics. For lamp monitoring and control system 600,
RF is the preferred communication link due to the costs required to
build the infrastructure for any of the other options.
[0081] FIG. 7 shows a monitoring and control system 700, according
to another embodiment of the invention, including a plurality of
base stations 610a-c, each having a plurality of associated
monitoring and control units 510a-h. Each base station 610a-c is
generally associated with a particular geographic area of coverage.
For example, the first base station 610a, communicates with
monitoring and control units 510a-c in a limited geographic area.
If monitoring and control units 510a-c are used for lamp monitoring
and control, the geographic area may consist of a section of a
city.
[0082] Although the example of geographic area is used to group
monitoring and control units 510a-c, it is well known to those
skilled in the art that other groupings may be used. For example,
to monitor and control remote devices 550 made by different
manufacturers, monitoring and control system 700 may use groupings
in which base station 610a services one manufacturer and base
station 610b services a different manufacturer. In this example,
bases stations 610a and 610b may be servicing overlapping
geographical areas.
[0083] FIG. 7 also shows a communication link between base stations
610a-c. This communication link is shown as a bus topology, but can
alternately be configured in a ring, star, mesh, or other topology.
An optional main station 710 can also be connected to the
communication link to receive and concentrate data from base
stations 610a-c. The media used for the communication link between
base stations 610a-c can be: RF, wire, coaxial cable, or fiber
optics.
[0084] FIG. 8 shows an example of a frequency channel plan for
communications between monitoring and control unit 510 and base
station 610 in monitoring and control system 600 or 700, according
to one embodiment of the invention. In this example table,
interactive video and data service (IVDS) radio frequencies in the
range of 218-219 MHz are shown. The IVDS channels in FIG. 8 are
divided into two groups, Group A and Group B, with each group
having nineteen channels spaced at 25 KHz steps. The first channel
of the group A frequencies is located at 218.025 MHz and the first
channel of the group B frequencies is located at 218.525 MHz.
[0085] FIGS. 9A-B show packet formats, according to two embodiments
of the invention, for packet data transferred between monitoring
and control unit 510 and base station 610. FIG. 9A shows a general
packet format, according to one embodiment of the invention,
including a start field 910, an ID field 912, a status field 914, a
data field 916, and a stop field 918.
[0086] Start field 910 is located at the beginning of the packet
and indicates the start of the packet.
[0087] ID field 912 is located after start field 910 and indicates
the ID for the source of the packet transmission and optionally the
ID for the destination of the transmission. Inclusion of a
destination ID depends on the system topology and geographic
layout. For example, if an RF transmission is used for the
communications link and if base station 610a is located far enough
from the other base stations so that associated monitoring and
control units 510a-c are out of range from the other base stations,
then no destination ID is required. Furthermore, if the
communication link between base station 610a and associated
monitoring and control units 510a-c uses wire or cable rather than
RF, then there is also no requirement for a destination ID.
[0088] Status field 914 is located after ID field 912 and indicates
the status of monitoring and control unit 510. For example, if
monitoring and control unit 510 is used in conjunction with street
lamps, status field 914 could indicate that the street lamp was
turned on or off at a particular time.
[0089] Data field 916 is located after status field 914 and
includes any data that may be associated with the indicated status.
For example, if monitoring and control unit 510 is used in
conjunction with street lamps, data field 916 may be used to
provide an A/D value for the lamp voltage or current after the
street lamp has been turned on.
[0090] Stop field 918 is located after data field 916 and indicates
the end of the packet.
[0091] FIG. 9B shows a more detailed packet format, according to
another embodiment of the invention, including a start byte 930, ID
bytes 932, a status byte 934, a data byte 936, and a stop byte 938.
Each byte comprises eight bits of information.
[0092] Start byte 930 is located at the beginning of the packet and
indicates the start of the packet. Start byte 930 will use a unique
value that will indicate to the destination that a new packet is
beginning. For example, start byte 930 can be set to a value such
as 02 hex.
[0093] ID bytes 932 can be four bytes located after start byte 930
which indicate the ID for the source of the packet transmission and
optionally the ID for the destination of the transmission. ID bytes
932 can use all four bytes as a source address which allows for
2.sup.32 (over 4 billion) unique monitoring and control units 510.
Alternately, ID bytes 932 can be divided up so that some of the
bytes are used for a source ID and the remainder are used for a
destination ID. For example, if two bytes are used for the source
ID and two bytes are used for the destination ID, the system can
include 2.sup.16 (over 64,000) unique sources and destinations.
[0094] Status byte 934 is located after ID bytes 932 and indicates
the status of monitoring and control unit 510. The status may be
encoded in status byte 934 in a variety of ways. For example, if
each byte indicates a unique status, then there exists 2.sup.8
(256) unique status values. However, if each bit of status byte 934
is reserved for a particular status indication, then there exists
only 8 unique status values (one for each bit in the byte).
Furthermore, certain combinations of bits may be reserved to
indicate an error condition. For example, a status byte 934 setting
of FF hex (all ones) can be reserved for an error condition.
[0095] Data byte 936 is located after status byte 934 and includes
any data that may be associated with the indicated status. For
example, if monitoring and control unit 510 is used in conjunction
with street lamps, data byte 936 may be used to provide an A/D
value for the lamp voltage or current after the street lamp has
been turned on.
[0096] Stop byte 938 is located after data byte 936 and indicates
the end of the packet. Stop byte 938 will use a unique value that
will indicate to the destination that the current packet is ending.
For example, stop byte 938 can be set to a value such as 03
hex.
[0097] FIG. 10 shows an example of bit location values for status
byte 934 in the packet format, according to another embodiment of
the invention. For example, if monitoring and control unit 510 is
used in conjunction with street lamps, each bit of the status byte
can be used to convey monitoring data.
[0098] FIG. 11A shows base station 1100 which includes an RX
antenna system 1110, a receiving system front end 1120, a
multi-port splitter 1130, a bank of RX modems 1140a-c, and a
computing system 1150.
[0099] RX antenna system 1110 receives RF monitoring data and can
be implemented using a single antenna or an array of interconnected
antennas depending on the topology of the system. For example, if a
directional antenna is used, RX antenna system 1110 may include an
array of four of these directional antennas to provide 360 degrees
of coverage.
[0100] Receiving system front end 1120 is coupled to RX antenna
system 1110 for receiving the RF monitoring data. Receiving system
front end 1120 can also be implemented in a variety of ways. For
example, a low noise amplifier (LNA) and pre-selecting filters can
be used in applications which require high receiver sensitivity.
Receiving system front end 1120 outputs received RF monitoring
data.
[0101] Multi-port splitter 1130 is coupled to receiving system
front end 1120 for receiving the received RF monitoring data.
Multi-port splitter 1130 takes the received RF monitoring data from
receiving system front end 1120 and splits it to produce split RF
monitoring data.
[0102] RX modems 1140a-c are coupled to multi-port splitter 1130
and receive the split RF monitoring data. RX modems 1140a-c each
demodulate their respective split RF monitoring data line to
produce a respective received data signal. RX modems 1140a-c can be
operated in a variety of ways depending on the configuration of the
system. For example, if twenty channels are being used, twenty RX
modems 1140 can be used with each RX modem set to a different fixed
frequency. On the other hand, in a more sophisticated
configuration, frequency channels can be dynamically allocated to
RX modems 1140a-c depending on the traffic requirements.
[0103] Computing system 1150 is coupled to RX modems 1140a-c for
receiving the received data signals. Computing system 1150 can
include one or many individual computers. Additionally, the
interface between computing system 1150 and RX modems 1140a-c can
be any type of data interface, such as RS-232 or RS-422 for
example.
[0104] Computing system 1150 includes an ID and status processing
unit (ISPU) 1152 which processes ID and status data from the
packets of monitoring data in the demodulated signals. ISPU 1152
can be implemented as software, hardware, or firmware. Using ISPU
1152, computing system 1150 can decode the packets of monitoring
data in the demodulated signals, or can simply pass, without
decoding, the packets of monitoring data on to another device, or
can both decode and pass the packets of monitoring data.
[0105] For example, if ISPU 1152 is implemented as software running
on a computer, it can process and decode each packet. Furthermore,
ISPU 1152 can include a user interface, such as a graphical user
interface, to allow an operator to view the monitoring data.
Furthermore, ISPU 1152 can include or interface to a database in
which the monitoring data is stored.
[0106] The inclusion of a database is particularly useful for
producing statistical norms on the monitoring data either relating
to one monitoring and control unit over a period of time or
relating to performance of all of the monitoring and control units.
For example, if the present invention is used for lamp monitoring
and control, the current draw of a lamp can be monitored over a
period of time and a profile created. Furthermore, an alarm
threshold can be set if a new piece of monitored data deviates from
the norm established in the profile. This feature is helpful for
monitoring and controlling lamps because the precise current
characteristics of each lamp can vary greatly. By allowing the
database to create a unique profile for each lamp, the problem
related to different lamp currents can be overcome so that an
automated system for quickly identifying lamp problems is
established.
[0107] FIG. 11B shows an alternate configuration for base station
1100, according to a further embodiment of the invention, which
includes all of the elements discussed in regard to FIG. 11A and
further includes a TX modem 1160, transmitting system 1162, and TX
antenna 1164. Base station 1100 as shown in FIG. 11B can be used in
applications which require a TX channel for control of remote
devices 550.
[0108] TX modem 1160 is coupled to computing system 1150 for
receiving control information. The control information is modulated
by TX modem 1160 to produce modulated control information.
[0109] Transmitting system 1162 is coupled to TX modem 1160 for
receiving the modulated control information. Transmitting system
1162 can have a variety of different configurations depending on
the application. For example, if higher transmit power output is
required, transmitting system 1162 can include a power amplifier.
If necessary, transmitting system 1162 can include isolators,
bandpass, lowpass, or highpass filters to prevent out-of-band
signals. After receiving the modulated control information,
transmitting system 1162 outputs a TX RF signal.
[0110] TX antenna 1164 is coupled to transmitting system 1162 for
receiving the TX RF signal and transmitting a transmitted TX RF
signal. It is well known to those skilled in the art that TX
antenna 1164 may be coupled with RX antenna system 1110 using a
duplexer for example.
[0111] FIG. 11C shows base station 1100 as part of a monitoring and
control system, according to another embodiment of the invention.
Base station 1100 has already been described with reference to FIG.
11A.
[0112] Additionally, computing system 1150 of base station 1100 can
be coupled to a communication link 1170 for communicating with a
main station 1180 or a further base station 1100a.
[0113] Communication link 1170 may be implemented using a variety
of technologies such as: a standard phone line, DDS line, ISDN
line, T1, fiber optic line, or RF link. The topology of
communication link 1170 can vary depending on the application and
can be: star, bus, ting, or mesh.
[0114] FIG. 12 shows a monitoring and control system 1200,
according to another embodiment of the invention, having a main
station 1230 coupled through a plurality of communication links
1220a-c to a plurality of respective base stations 1210a-c.
[0115] Base stations 1210a-c can have a variety of configurations
such as those shown in FIGS. 11A-B. Communication links 1220a-c
allow respective base stations 1210a-c to pass monitoring data to
main station 1230 and to receive control information from main
station 1230. Processing of the monitoring data can either be
performed at base stations 1210a-c or at main station 1230.
[0116] FIG. 13 shows a base station 1300 which is coupled to a
communication server 1340 via a communication link 1330, according
to another embodiment of the invention. Base station 1300 includes
an antenna and preselector system 1305, a receiver modem group
(RMG) 1310, and a computing system 1320.
[0117] Antenna and preselector system 1305 are similar to RX
antenna system 1110 and receiving system front end 1120 which were
previously discussed. Antenna and preselector system 1305 can
include either one antenna or an array of antennas and preselection
filtering as required by the application. Antenna and preselector
system 1305 receives RF monitoring data and outputs preselected RF
monitoring data.
[0118] Receiver modem group (RMG) 1310 includes a low noise pre-amp
1312, a multi-port splitter 1314, and several RX modems 1316a-c.
Low noise pre-amp 1312 receives the preselected RF monitoring data
from antenna and preselector system 1305 and outputs amplified RF
monitoring data.
[0119] Multi-port splitter 1314 is coupled to low noise pre-amp
1312 for receiving the amplified RF monitoring data and outputting
split RF monitoring data lines.
[0120] RX modems 1316a-c are coupled to multi-port splitter 1314
for receiving and demodulating one of the split RF monitoring data
lines and outputting received data (RXD) 1324, received clock (RXC)
1326, and carrier detect (CD) 1328. These signals can use a
standard interface such as RS-232 or RS-422 or can use a
proprietary interface.
[0121] Computing system 1320 includes at least one base site
computer 1322 for receiving RXD, RXC, and CD from RX modems
1316a-c, and outputting a serial data stream.
[0122] Computing system 1320 further includes an ID and status
processing unit (ISPU) 1323 which processes ID and status data from
the packets of monitoring data in RXD. ISPU 1323 can be implemented
as software, hardware, or firmware. Using ISPU 1323, computing
system 1320 can decode the packets of monitoring data in the
demodulated signals, or can simply pass, without decoding, the
packets of monitoring data on to another device in the serial data
stream, or can both decode and pass the packets of monitoring
data.
[0123] Communication link 1330 includes a first communication
interface 1332, a second communication interface 1334, a first
interface line 1336, a second interface line 1342, and a link
1338.
[0124] First communication interface 1332 receives the serial data
stream from computing system 1320 of base station 1300 via first
interface line 1336. First communication interface 1332 can be
co-located with computing system 1320 or be remotely located. First
communication interface 1332 can be implemented in a variety of
ways using, for example, a CSU, DSU, or modem.
[0125] Second communication interface 1334 is coupled to first
communication interface 1332 via link 1338. Link 1338 can be
implemented using a standard phone line, DDS line, ISDN line, T1,
fiber optic line, or RF link. Second communication interface 1334
can be implemented similarly to first communication interface 1332
using, for example, a CSU, DSU, or modem.
[0126] Communication link 1330 outputs communicated serial data
from second communication interface 1334 via second communication
line 1342.
[0127] Communication server 1340 is coupled to communication link
1330 for receiving communicated serial data via second
communication line 1342. Communication server 1340 receives several
lines of communicated serial data from several computing systems
1320 and multiplexes them to output multiplexed serial data on to a
data network. The data network can be a public or private data
network such as an internet or intranet.
[0128] FIGS. 14A-E show methods for implementation of logic for
lamp monitoring and control system 600, according to a further
embodiment of the invention.
[0129] FIG. 14A shows one method for energizing and de-energizing a
street lamp and transmitting associated monitoring data. The method
of FIG. 14A shows a single transmission for each control event. The
method begins with a start block 1400 and proceeds to step 1410
which involves checking AC and Daylight Status. The Check AC and
Daylight Status step 1410 is used to check for conditions where the
AC power and/or the Daylight Status have changed. If a change does
occur, the method proceeds to step 1420 which is a decision block
based on the change.
[0130] If a change occurred, step 1420 proceeds to a Debounce Delay
step 1422 which involves inserting a Debounce Delay. For example,
the Debounce Delay may be 0.5 seconds. After Debounce Delay step
1422, the method leads back to Check AC and Daylight Status step
1410.
[0131] If no change occurred, step 1420 proceeds to step 1430 which
is a decision block to determine whether the lamp should be
energized. If the lamp should be energized, then the method
proceeds to step 1432 which turns the lamp on. After step 1432 when
the lamp is turned on, the method proceeds to step 1434 which
involves Current Stabilization Delay to allow the current in the
street lamp to stabilize. The amount of delay for current
stabilization depends upon the type of lamp used. However, for a
typical vapor lamp a ten minute stabilization delay is appropriate.
After step 1434, the method leads back to step 1410 which checks AC
and Daylight Status.
[0132] Returning to step 1430, if the lamp is not to be energized,
then the method proceeds to step 1440 which is a decision block to
check to deenergize the lamp. If the lamp is to be deenergized, the
method proceeds to step 1442 which involves turning the Lamp Off.
After the lamp is turned off, the method proceeds to step 1444 in
which the relay is allowed a Settle Delay time. The Settle Delay
time is dependent upon the particular relay used and may be, for
example, set to 0.5 seconds. After step 1444, the method returns to
step 1410 to check the AC and Daylight Status.
[0133] Returning to step 1440, if the lamp is not to be
deenergized, the method proceeds to step 1450 in which an error bit
is set, if required. The method then proceeds to step 1460 in which
an A/D is read.
[0134] The method then proceeds from step 1460 to step 1470 which
checks to see if a transmit is required. If no transmit is
required, the method proceeds to step 1472 in which a Scan Delay is
executed. The Scan Delay depends upon the circuitry used and, for
example, may be 0.5 seconds. After step 1472, the method returns to
step 1410 which checks AC and Daylight Status.
[0135] Returning to step 1470, if a transmit is required, then the
method proceeds to step 1480 which performs a transmit operation.
After the transmit operation of step 1480 is completed, the method
then returns to step 1410 which checks AC and Daylight Status.
[0136] FIG. 14B is analogous to FIG. 14A with one modification.
This modification occurs after step 1420. If a change has occurred,
rather than simply executing step 1422, the Debounce Delay, the
method performs a further step 1424 which involves checking whether
daylight has occurred. If daylight has not occurred, then the
method proceeds to step 1426 which executes an Initial Delay. This
initial delay may be, for example, 0.5 seconds. After step 1426,
the method proceeds to step 1422 and follows the same method as
shown in FIG. 14A.
[0137] Returning to step 1424 which involves checking whether
daylight has occurred, if daylight has occurred, the method
proceeds to step 1428 which executes an Initial Delay. The Initial
Delay associated with step 1428 should be a significantly larger
value than the Initial Delay associated with step 1426. For
example, an Initial Delay of 45 seconds may be used. The Initial
Delay of step 1428 is used to prevent a false triggering which
deenergizes the lamp. In actual practice, this extended delay can
become very important because if the lamp is inadvertently
deenergized too soon, it requires a substantial amount of time to
reenergize the lamp (for example, ten minutes). After step 1428,
the method proceeds to step 1422 which executes a Debounce Delay
and then returns to step 1410 as shown in FIGS. 14A and 14B.
[0138] FIG. 14C shows a method for transmitting monitoring data
multiple times in monitoring and control unit 510, according to a
further embodiment of the invention. This method is particularly
important in applications in which monitoring and control unit 510
does not have a RX unit 540 for receiving acknowledgments of
transmissions.
[0139] The method begins with a transmit start block 1482 and
proceeds to step 1484 which involves initializing a count value,
i.e. setting the count value to zero. The method proceeds from step
1484 to step 1486 which involves setting a variable x to a value
associated with a serial number of monitoring and control unit 510.
For example, variable x may be set to 50 times the lowest nibble of
the serial number.
[0140] The method proceeds from step 1486 to step 1488 which
involves waiting a reporting start time delay associated with the
value x. The reporting start time is the amount of delay time
before the first transmission. For example, this delay time may be
set to x seconds where x is an integer between 1 and 32,000 or
more. This example range for x is particularly useful in the street
lamp application since it distributes the packet reporting start
times over more than eight hours, approximately the time from
sunset to sunrise.
[0141] The method proceeds from step 1488 to step 1490 in which a
variable y representing a channel number is set. For example, y may
be set to the integer value of RTC/12.8, where RTC represents a
real time clock counting from 0-255 as fast as possible. The RTC
may be included in processing and sensing unit 520.
[0142] The method proceeds from step 1490 to step 1492 in which a
packet is transmitted on channel y. Step 1492 proceeds to step 1494
in which the count value is incremented. Step 1494 proceeds to step
1496 which is a decision block to determine if the count value
equals an upper limit N.
[0143] If the count is not equal to N, the method returns from step
1496 to step 1488 and waits another delay time associated with
variable x. This delay time is the reporting delta time since it
represents the time difference between two consecutive reporting
events.
[0144] If the count is equal to N, the method proceeds from step
1496 to step 1498 which is an end block. The value for N must be
determined based on the specific application. Increasing the value
of N decreases the probability of a unsuccessful transmission since
the same data is being sent multiple times and the probability of
all of the packets being lost decreases as N increases. However,
increasing the value of N increases the amount of traffic which may
become an issue in a monitoring and control system with a plurality
of monitoring and control units.
[0145] FIG. 14D shows a method for transmitting monitoring data
multiple times in a monitoring and control system according to a
another embodiment of the invention.
[0146] The method begins with a transmit start block 1410' and
proceeds to step 1412' which involves initializing a count value,
i.e., setting the count value to 1. The method proceeds from step
1412' to step 1414' which involves randomizing the reporting start
time delay. The reporting start time delay is the amount of time
delay required before the transmission of the first data packet. A
variety of methods can be used for this randomization process such
as selecting a pseudo-random value or basing the randomization on
the serial number of monitoring and control unit 510.
[0147] The method proceeds from step 1414' to step 1416' which
involves checking to see if the count equals 1. If the count is
equal to 1, then the method proceeds to step 1420' which involves
setting a reporting delta time equal to the reporting start time
delay. If the count is not equal to 1, the method proceeds to step
1418' which involves randomizing the reporting delta time. The
reporting delta time is the difference in time between each
reporting event. A variety of methods can be used for randomizing
the reporting delta time including selecting a pseudo-random value
or selecting a random number based upon the serial number of the
monitoring and control unit 510.
[0148] After either step 1418' or step 1420', the method proceeds
to step 1422' which involves randomizing a transmit channel number.
The transmit channel number is a number indicative of the frequency
used for transmitting the monitoring data. There are a variety of
methods for randomizing the transmit channel number such as
selecting a pseudo-random number or selecting a random number based
upon the serial number of the monitoring and control unit 510.
[0149] The method proceeds from step 1422' to step 1424' which
involves waiting the reporting delta time. It is important to note
that the reporting delta time is the time which was selected during
the randomization process of step 1418' or the reporting start time
delay selected in step 1414', if the count equals 1. The use of
separate randomization steps 1414' and 1418' is important because
it allows the use of different randomization functions for the
reporting start time delay and the reporting delta time,
respectively.
[0150] After step 1424' the method proceeds to step 1426' which
involves transmitting a packet on the transmit channel selected in
step 1422'.
[0151] The method proceeds from step 1426' to step 1428' which
involves incrementing the counter for the number of packet
transmissions.
[0152] The method proceeds from step 1428' to step 1430' in which
the count is compared with a value N which represents the maximum
number of transmissions for each packet. If the count is less than
or equal to N, then the method proceeds from step 1430' back to
step 1418' which involves randomizing the reporting delta time for
the next transmission. If the count is greater than N, then the
method proceeds from step 1430' to the end block 1432' for the
transmission method.
[0153] In other words, the method will continue transmission of the
same packet of data N times, with randomization of the reporting
start time delay, randomization of the reporting delta times
between each reporting event, and randomization of the transmit
channel number for each packet. These multiple randomizations help
stagger the packets in the frequency and time domain to reduce the
probability of collisions of packets from different monitoring and
control units.
[0154] FIG. 14E shows a further method for transmitting monitoring
data multiple times from a monitoring and control unit 510,
according to another embodiment of the invention.
[0155] The method begins with a transmit start block 1440' and
proceeds to step 1442' which involves initializing a count value,
i.e., setting the count value to 1. The method proceeds from step
1442' to step 1444' which involves reading an indicator, such as a
group jumper, to determine which group of frequencies to use, Group
A or B. Examples of Group A and Group B channel numbers and
frequencies can be found in FIG. 8.
[0156] Step 1444' proceeds to step 1446' which makes a decision
based upon whether Group A or B is being used. If Group A is being
used, step 1446' proceeds to step 1448' which involves setting a
base channel to the appropriate frequency for Group A. If Group B
is to be used, step 1446' proceeds to step 1450' which involves
setting the base channel frequency to a frequency for Group B.
[0157] After either Step 1448' or step 1450', the method proceeds
to step 1452' which involves randomizing a reporting start time
delay. For example, the randomization can be achieved by
multiplying the lowest nibble of the serial number of monitoring
and control unit 510 by 50 and using the resulting value, x, as the
number of milliseconds for the reporting start time delay.
[0158] The method proceeds from step 1452' to step 1454' which
involves waiting x number of seconds as determined in step
1452'.
[0159] The method proceeds from step 1454' to step 1456' which
involves setting a value z=0, where the value z represents an
offset from the base channel number set in step 1448' or 1450'.
Step 1456' proceeds to step 1458' which determines whether the
count equals 1. If the count equals 1, the method proceeds from
step 1458' to step 1472' which involves transmitting the packet on
a channel determined from the base channel frequency selected in
either step 1448' or step 1450' plus the channel frequency offset
selected in step 1456'.
[0160] If the count is not equal to 1, then the method proceeds
from step 1458' to step 1460' which involves determining whether
the count is equal to N, where N represents the maximum number of
packet transmissions. If the count is equal to N, then the method
proceeds from step 1460' to step 1472' which involves transmitting
the packet on a channel determined from the base channel frequency
selected in either step 1448' or step 1450' plus the channel number
offset selected in step 1456'.
[0161] If the count is not equal to N, indicating that the count is
a value between 1 and N, then the method proceeds from step 1460'
to step 1462' which involves reading a real time counter (RTC)
which may be located in processing and sensing unit 412.
[0162] The method proceeds from step 1462' to step 1464' which
involves comparing the RTC value against a maximum value, for
example, a maximum value of 152. If the RTC value is greater than
or equal to the maximum value, then the method proceeds from step
1464' to step 1466' which involves waiting x seconds and returning
to step 1462'.
[0163] If the value of the RTC is less than the maximum value, then
the method proceeds from step 1464' to step 1468' which involves
setting a value y equal to a value indicative of the channel number
offset. For example, y can be set to an integer of the real time
counter value divided by 8, so that Y value would range from 0 to
18.
[0164] The method proceeds from step 1468' to step 1470' which
involves computing a frequency offset value z from the channel
number offset value y. For example, if a 25 KHz channel is being
used, then z is equal to y times 25 KHz.
[0165] The method then proceeds from step 1470' to step 1472' which
involves transmitting the packet on a channel determined from the
base channel frequency selected in either step 1448' or step 1450'
plus the channel frequency offset computed in step 1470'.
[0166] The method proceeds from step 1472' to step 1474' which
involves incrementing the count value. The method proceeds from
step 1474' to step 1476' which involves comparing the count value
to a value N+1 which is related to the maximum number of
transmissions for each packet. If the count is not equal to N+1,
the method proceeds from step 1476' back to step 1454' which
involves waiting x number of milliseconds. If the count is equal to
N+1, the method proceeds from step 1476' to the end block
1478'.
[0167] The method shown in FIG. 14E is similar to that shown in
FIG. 14D, but differs in that it requires the first and the Nth
transmission to occur at the base frequency rather than a randomly
selected frequency.
[0168] The foregoing embodiments are merely exemplary and are not
to be construed as limiting the present invention. The present
teaching can be readily applied to other types of apparatuses. The
description of the present invention is intended to be
illustrative, and not to limit the scope of the claims. Many
alternatives, modifications, and variations will be apparent to
those skilled in the art.
* * * * *